Effects of between invasive lionfish and native Nassau grouper

Report
Interactions Between Invasive
Lionfish and Native Nassau Grouper
Wendel Raymond
Dr. Mark Hixon
Mark Albins
Tim Pusack
Kurt Ingemen
OSU HHMI 2010
The Indo-Pacific Lionfish (Pterois volitans)
•
•
•
•
Native to the Indo-Pacific
Maximum observed size: 38cm
Maximum observed depth: 55m
Average density: 80 individuals per
hectare
• Eat fish and crustaceans
• First sighted in southern Florida in late
1980’s and early 1990’s.
Lionfish in the Invaded Range
•
•
•
•
Maximum observed size: 45cm
Maximum observed depth: 300m
Densities range from 21-390 individuals per hectare
Lionfish can reduce native juvenile reef fish abundances by 79%.
Nassau Grouper (Epinephelus striatus)
• Nassau grouper is a native
predator on Atlantic reefs
• Important to commercial
and subsistence fisheries
• Little is known of the effects
lionfish may have on Nassau
groupers and vice versa
• Possible biological control
Questions
• Do lionfish and Nassau grouper
compete for shelter?
• Do large lionfish eat small Nassau
grouper?
• Do large Nassau grouper eat small
lionfish?
Perry Institute for Marine Science
Lee Stocking
Island
Exuma Sound,
Bahamas
Methods
• Experiments were conducted in large in-ground tanks.
• Single lionfish and Nassau grouper were placed in partitioned cage for a
24hr acclimation period.
• Morning, midday and evening, positions were recorded so that distance
from shelter could be measured.
• Three treatments at size ratios of 1:1, 1:4, 3:1 (lionfish:Nassau grouper).
• Cinderblocks were used for shelter.
1 meter
Methods
• After acclimation period, partitions and
outer cinderblocks were removed.
• Recorded movements and behavior for 20
min.
• Morning, midday and evening, positions
were recorded so that distance from shelter
could be measured.
Data Analysis
Comparing random expected distance to observed distance
1:1
Frequency
Before
After
Distance From Shelter (m)
1:4
Data Analysis
Comparing random expected distance to observed distance
1:1
Frequency
Before
After
Distance From Shelter (m)
1:4
Results
Comparing random expected distance to observed distance
1:1
Frequency
Before
After
p-value <0.05
p-value <0.01
Distance From Shelter (m)
1:4
Results
Comparing before and after percentage of observations in shelter
Percentage of time spent in shelter hole for 1:1 Treatment
Before
Lionfish
22.2%
Nassau Grouper
81.0%


After
p-value
14.3%
0.310
63.2%
0.159
Percentage of time spent in shelter hole for 1:4 Treatment
Before
After
p-value
Lionfish
52.2%

58.9%
0.419
Nassau Grouper
65.6%

39.3%
0.137
Results
Predation
Large Lionfish with Small Grouper
(3:1 Treatment)
Number of Predation events
8
7
6
5
4
3
2
1
0
0
E. striatus
Halichoeres bivittatus
Haemulon sp.
Results
Predation
Large Grouper with Small
Lionfish
(1:4 Treatment)
Number of Predation events
8
7
6
5
4
3
2
1
0
0
P. volitans
Halichoeres bivittatus
Conclusions
• Do lionfish and Nassau grouper compete for shelter?
-Yes – Nassau grouper shifted away from shelter in the
presence of lionfish
• Do large lionfish eat small Nassau grouper?
-No – even though they quickly ate other species
• Do large Nassau groupers eat small lionfish?
-No – even though they quickly ate other species
Future Research
• Growth and persistence of
lionfish and Nassau grouper
when in the presence vs. absence
of each other in the wild.
• Why don’t lionfish eat small
Nassau groupers?
• Why don’t Nassau grouper eat
small lionfish?
Acknowledgments
Howard Hughes Medical Institute
Oregon State University URISC Program
Dr. Kevin Ahern
Dr. Mark Hixon
Tim Pusack
Mark Albins
Kurt Ingemen
Julia Lawson
Sean Hixon
Perry Institute for Marine Science Staff and Interns
Hixon Lab Bahamas Team 2010
Mean Distance From Shelter in 1:4 Treatment
Lionfish
Nassau Grouper
Before Removal
6.1cm
6.2cm
After Removal
21.0cm
45.6cm

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